Many of the early inventors of the typewriter thought that what they were inventing was a prosthetic device for the blind. Why would ordinary writers need a writing machine? They had pens. Eventually, it became clear that such a mechanism could benefit the seeing, too, but, as we find out in "The Iron Whim: A Fragmented History of Typewriting" (Cornell; $29.95), by Darren Wershler-Henry, a professor of communication studies in Ontario, almost two centuries, roughly the eighteenth and the nineteenth, passed before that hope was realized. There was no single moment of discovery, no lone inventor crying "Eureka!" in a darkened laboratory. On the contrary, historians estimate that the typewriter was invented at least fifty-two times, as one tinkerer after another groped toward a usable design. One early writing mechanism looks like a birthday cake, another like a pinball machine. One was almost eight feet tall; another, a Tyrolean entry, was whittled largely from wood. Until about the eighteen-thirties, all typewriters lacked a keyboard, and when they got one it was usually modelled on that of the piano. Nor did they have a ribbon. That didn't make its appearance until 1841; in most earlier machines the keys were inked by rollers or carbon paper.